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Sub-nanometer probes of surfaces provide important information about chemical and physical properties of materials at atomic level.  Microwave microscopy (left) is used to study materials properties at GHz (109 sec-1). This is the frequency range relevant for computers and cell phones, for which the materials are being explored. We show for the first time that one can image atoms at this frequency (right).

Background: A bar magnet has two poles, denoted as +1 and -1 magnetic charges.  Patterned structures consist of many magnets (Fig. 1), where the square array (Fig. 1a) does not, whereas the honeycomb (Fig. 1b) has, net magnetic charges (or magnetic monopoles).  Under a magnetic field these local magnetic monopoles will move (Fig. 1c).  This latter structure is called “spin ice”, because it has a large number of nearly degenerate configurations.

In crystalline materials, topologial defects such as dislocations mark flow defects, or “soft spots,” corresponding to local regions that are likely to rearrange due to thermal fluctuations or an applied load.  In disordered packings, it is extremely difficult to identify the corresponding soft spots. We previously discovered that sound waves are strongly scattered by flow defects, enabling us to identify soft spots acoustically.

Liquid crystals are soft materials which see frequent use in optical displays and other smart devices. This is because they can change their optical properties (such as light transmission and polarization) when an electric field is applied. This allows them to selectively block or transmit light, creating the pixels that form images on the screen. Similarly, nanoparticles are materials that can have different optical properties that depend on their size. In this work, Penn researchers have developed new liquid crystal-nanoparticle hybrid systems. They have integrated specially synthesized molecules known as “dendritic promesogenic ligands” that can attach to the nanoparticles.  

Cool and Creative Chemistry is one of the interactive classes  of the LCMRC Materials Science from CU  K-12 outreach program. MSFCU presentations, designed by Center faculty and students, have been presented to 65,000 Colorado children over the past 10 years. The photo was taken during a presentation at Super Science Saturday at the Steelworks Museum of Industry & Culture in Pueblo, Colorado.  Photo: John Jaques/Pueblo

We have developed analytic methods that establish molecular constraints to photochemical efficiency in the engineering and construction of molecular photochemical materials and devices useful to addressing the global energy challenge. The absence, to-date, of analytic procedures has seriously handicapped progress in the development of photochemical devices. The new methods will provide important precise engineering guidelines to photochemical device construction in the future.

Ferroelectric tunnel junctions exploit an ultrathin ferroelectric layer, 100,000 times thinner than a sheet of paper, so that electrons can "tunnel" through it. This layer resides between two metal electrodes that can reverse the direction of its polarization by applying electric voltage to it. A junction polarity determines its resistance to tunneling current, with one direction allowing current to flow and the other strongly reducing it, known as “on” and “off” states.

Micron-sized non-volatile magnetoresistance devices are being pursued using ferroelectric/magnetostrictive multilayers.

Metamaterials are engineered structures with novel electromagnetic properties such as artificial magnetism, negative refraction, and cloaking. Thus far, most metamaterial designs have been limited to fixed, narrow frequency range of operation determined by the size of the constitutive resonator elements. Work within the NSF funded Center for the